The present invention relates, in general, to electronics, and more particularly, to methods of forming semiconductor devices and structure.
In the past, the semiconductor industry utilized various methods and structures to produce variable frequency oscillators. One particular oscillator implementation, referred to as a saw-tooth oscillator, was used in various applications. Saw-tooth oscillators generally charged a capacitor with current sources and used the voltage across the capacitor as the output signal or oscillating signal. One problem with the variable frequency saw-tooth oscillator implementations was the linearity of changes in the frequency of the oscillating signal resulting from changes in a frequency control signal. This relationship is referred to hereinafter as control linearity. The saw-tooth oscillator typically had internal delays that affected the period of the oscillating frequency. At low frequencies, the delay within the oscillator was a small part of the oscillation period. At high frequencies the delay became a more significant portion of the period and resulted in poor control linearity.
Accordingly, it is desirable to have an oscillator that has a more constant control linearity over the oscillator frequency range.
For simplicity and clarity of illustration, elements in the figures are not necessarily to scale, and the same reference numbers in different figures denote the same elements. Additionally, descriptions and details of well known steps and elements are omitted for simplicity of the description. As used herein current carrying electrode means an element of a device that carries current through the device such as a source or a drain of an MOS transistor or an emitter or a collector of a bipolar transistor, and a control electrode means an element of the device that controls current through the device such as a gate of an MOS transistor or a base of a bipolar transistor. Although the devices are explained herein as certain P-Channel and N-channel devices, a person of ordinary skill in the art will appreciate that complementary devices are also possible in accordance with the present invention.